Weld rod



United States Patent now Patent No. 2,588,700, dated March 11, 1952. Divided and this application May 2, 1950, Serial No.

Claims. (Cl. 219-8) This invention relates to welding and more particularly to improvements adapted for advantageous use in the welding of corrosion resistant steels of high chromium content.

The invention is further concerned with such Welding developments which have proven successful in the manufacture of pressure vessel appurtenances and other equipment adapted for use in systems involving corrosive fluids at temperatures in the steel embrittlement range (600 F.

to 1000 F.).

n An object of the invention is to present welding improverhents involving welds constructed in a novel manher and capable of long continued use in pressure vessel equi ment subjected to service temperatures within the above range.

' A more specific object of the invention is to present a duplex metal weld of such characteristics that even the maximum embrittlement involved in the pertinent equipment in service will not reduce the toughness or ductility of the Weld to a hazardous degree.

A further object of the invention is to provide flux coated weldrods which are particularly adapted for the arc welding of alloy steels of high corrosion resistance.

Another object of the invention is a welding flux mixture which is productive of improved results in welding of alloy steels which have extreme air hardening and crack sensitivity characteristics.

The invention will be described with reference to the accompanying drawings, and other objects of the invention will appear as the description proceeds.

In the drawings:

Fig. l is a sectional view through a header and tube combination, the parts ofwhich are joined by the use of the invention;

- Fig. 2 is a fragmentary section of the Fig. 1 structure on an enlarged scale;

Fig. 3 is a view illustrating the flux coated weldrod employed in the welding of corrosion resistant steels of high chromium content; and

Fig. 4 is a view showing a flux coated weldrod employed in the welding of an alloy steel of lower chromium content, but less susceptible to embrittlement at service temperatures in the range of 600 F. to 1000 F.

Fig. 1 of the drawings illustrates a header and a section of a tube 12 united by a circular weld 14. The tube and the header are of chrome iron of high chromium content and high corrosion resistance, and the combination is intended to be illustrative of welded components of various shapes and dimensions, but all are particularly adapted for advantageous use in pressure vessels of fluid heat exchange installations subject internally to corrosive fluids at service temperature ranges of 600 F. to 1000 F.

Tube 12 and header 10 are united by the root beads 16 and 18 deposited in a giOoV formed by these elements and the backing up ring 20, by electric arc welding employing a weldrod such as that indicated in Fig. 3. The composition of this weldrod is of an alloy steel involving a nickel content of the order of 4%, and a chromium content comparable to that of the tube and the header. Furthermore, the crack sensitivity of the high chromium content weld metal, and the extreme air hardening characteristic of the latter are alleviated by the lime-titanium flux coating 24 of the weldrod 22. This flux coating may have a lime content of the order of 25-56% and a titanium oxide content of the order 2,697,770 Patentercl Dec. 21, 1954 ice 0-30%, in an equivalent percentage analysis.

In such an analysis the other ingredients of the coating may involve the following elements or compounds in the indicated ranges of equivalent percentages;

, I Percent SiOz 20-35 Fe2O 2- 8 A1203 Q- 6 MgO 0- 5 F -4 CO2 -a 11-22 MnsQ4 3-10 NazO 2- 6 For the 27 chromium-4 nickel weldrod shown, coatings having the following equivalent percentages have been found to coact with the other elements of the welding to produce excellent results:

After the beads 16 and 18 of the 27 Cr-4 Ni are formed, the remainder of the weld 14 is formed by the use of the coated weldrod 26, of an alloy known as Croloy 7. This terminology springs from the fact that chromium content of the weld metal of the weldrod is of the order of 7%. It also has approximately /2 of 1% of molybdenum. This weldrod preferably has a lime-titania coating indicated in Fig. 4.

This coating has the following analysis:

Equivalent percentages of:

SiOz 2 F6203 Tioz However, the range of the equivalent percentages of the components of this coating is similar to the range of percentages given with respect to the coating employed on the weldrod 22 shown in Fig. 3.

The weldrod indicated in Fig. 4 of the drawings is of the following analysis:

Percent C 0.08 Mn 0.46 Si 0.55 Cr 7.16 S 0.018 P a. 0020 Mo 0.47 Fe Remainder However, the range of elements in this composition may vary as indicated below:

Percent C 0.10-Max. Mn 0.40-0.60 Si 0.40-0.60 Cr 6.00-8.00 Mo 0.40-0.60 S 0.025-Max. P 0.025-Max. Fe Remainder The 27 chrome-iron of the header 10 and the tube 12,

and the 27 Cr-4 Ni weld metal of the beads 16 and 18,

balance iron and incidental impurities; and a flux coating on said core having the following composition in equivalent percentages Percent are subject to embrittlement when cooled slowly through, MgO to or held at temperatures of about 600 F. to l000 F. F 5 to 25 When such temperature ranges are encountered in service CO2 11 to 22 conditions, the consequent embrittlement of the high 5 MnaOr 3 to chrome metal would result in an unsafe weld, due to its NazO 2 to 6 lack of toughness. In the present invention, this difiiculty CaO 25 to 50 is overcome by the formation of the main body of the CrzOa 0 to 0.3 wgldlby the electrtizifusilonhdeposition of %he Ciitlaloy 7 sltleel 1 TiOz 0 to 30 w ic givest ewe a ig percentageo toug ness,w en 0 the weld structure is properly heat treated. Heating the A flux coated m weldnlg rod for l finished weld 14 to 13750 F followed by watel. quench ing alloy steels of high corros onresistance hav ng high mg or other methods of cooling Softens the weld air hardening and crack sens1t1v1ty characteristics, sa1d hardened Croloy 7 (or 7 CPI/2 Weld metal and rod comprising a core having the following composition imparts to the weld embrittled root beads 16 and 18 (27 Percent Cr-4 Ni) and to the heat affected 27 chromium-iron of Carbon 0.10 to 0.15 the header 10 and the tube 12, a relatively high degree Manganese 0.60 to 0.70 of toughness. In service involving temperature ranges Silicon 0.40 to 0.60 from 600 F. to 1000 F., there will be embrittlement in Chromium 28.00 to 30.00 only the 27 Cr-4 Ni weld metal and the 27 chromiurn- 20 Nickel 3.50 to 4.50 iron base metal, and the latter more than the former. The Nitrogen 0.15 to 0.17 7 Cr /2Mo weld metal retains its original ductility. b 1 d However, the Weld, as a whole, retains, after considerable a W 9& mclqental unpuntlqs and a l service, a toughness greater than that of the 27 chromemg Sal Cole having the followmg compos1t1on m iron of the base metal of the header and the tube remote equlva em Percentages from the weld. Percent It is to be noted that the above described heat treat- E ment involves a quick cooling through the carbide form- 3 ing temperature range of the 27 Cr-4 Ni root beads 16 6 and 18. With this treatment the formation of chromium 30 C 8 4 carbide in the root heads is minimized or substantially 0 eliminated because there is insufficient time for its formag tion to any substantial degree. This application is a division of the parent application CO2 Serial No. 607,173, filed on July 26, 1945, now Patent No. Nam 2,588,700, issued March 11, 1952, and is a continuation GU03 0f applicatlon Seflal 694,681, filed September 4. A flux coated metallic arc welding rod for are weld- 9 I1 0W abaHd011eding alloy steels of high corrosion resistance having high I claim: air hardening and crack sensitivity characteristics, said ing1.a111\o glls iegsatgg 1 1 531 22); gs ix r e s igtgge i lgi n g fi gl; 40 rod comprising a core having the following compos1t1on air hardening and crack sensitivity characteristics, said Percent rod comprising a core with a chromium content of from calbon to 20% to 30% and a nickel content of from 2% to 5%, Manganese to with the balance principally iron and incidental irnpuslhcon. to rities; and a flux coating on said core having the following chromlum 28-00 to 3000 composition in equivalent percentages Nickel to Percmt Nltrogen 0.15 to 0.17 S 2 20 to 33 balance iron and incidental impurities; and a flux coating F62 3 2 t0 8 50 on said core having the following composition in equiviaxlaga 8: g alent percentages g 0 Percent F 25 SiOa 22.9 CO2 11t022 F6203 3.7 MI1304 3t010 TiQz 4.3 N320 2 t0 6 A1203 0.5 C30 25 t0 5 M11304 3.4 CrzOa H 03 CaO 39.0 TiO2 0' 0 3 MgO 2.0 2. A flux coated metallic arc welding rod for are weld- F ing alloy steels of high corrosion resistance having high CO2 air hardening and crack sensitivity characteristics, said Nazo rod compllslng a Core havlng the followlng compos1t1on 5. A flux coated metallic arc welding rod for arc welding alloy steels of high corrosion resistance having high Percent s. Carbon 010 to 0.15 an harden ng and crack sensitivity characteristics, sa1d Manganese 060 to 070 rod comprising a core w1th a chrornlum content of from Silicon 040 to 060 20% to 30% and a n1ckel content of from 2% to 5%, Chromium 2800 to 3000 with the balance principally iron and incidental impu- Nickel 350 to 450 To rities; and a flux coating on sa d core including equiv- Nitrogen 015 to 0.17 alent percentages of the following constltuents:

Percent SiOz 20 to 35 CO2 11 to 22 CaO 25 to 50 TiOz 0 to 30 No references cited. 

1. A FLUX COATED METALLIC ARC WELDING ROD FOR ARC WELDING ALLOY STEELS OF HIGH CORROSION RESISTANCE HAVING HIGH AIR HARDENING AND CRACK SENSITIVITY CHARACTERISTICS, SAID ROD COMPRISING A CORE WITH A CHROMIUM CONTENT OF FROM 20% TO 30% AND A NICKEL CONTENT OF FROM 2% TO 5%, WITH THE BALANCE PRINCIPALLY IRON AND INCIDENTAL UMPURITIES; AND A FLUX COATING ON SAID CORE HAVING THE FOLLOWING COMPOSITION IN EQUIVALENT PERCENTAGES 